Archive for the ‘Do It Yourself’ Category:

2019-10-05 Huge Corcom Filters For RFI

from FB group post to Building Transistor Radios 2019 Oct 5 I spent quite a bit of time adding filtering to my 0 to 30VDC, 10A SMPS to get rid of the RF interference. It was successful, I got rid of most of it, but not all. So I think I found the solution. This

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2019-09-09 Zenith Royal 475 Information

more text below Zenith Royal 475 ARF project & service info links: https://antiqueradios.com/forums/viewtopic.php?f=4&t=233319 https://www.antiqueradios.com/forums/viewtopic.php?f=4&t=226370 https://www.antiqueradios.com/forums/viewtopic.php?f=4&t=235052 The Zenith factory schematic and PCB layout is located on page 185 of the Beitmans service literature which is freely available on-line: https://www.americanradiohistory.com/Archive-Rider/BEITMAN-SUPREME/Beitman-1961.pdf ** also posted to FB group vintage transistor radios Usually the capacitors are the problem. There are

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2019-07-06 Earliest Audio Amplifiers I built

from FB group Building Transistor Radios July 6 Bill Korbak The early germanium alloy transistors didn’t have enough bandwidth for RF, they were only good for audio. That’s where I built my first amplifier, a three transistor audio amp on a PC board I etched in ferric chloride. I also built the power amplifier. It

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2019-06-12 Plug-in Coils Pros And Cons

from FB group Regenerative Radio… Jun 13 I’ve thought about using plug-in coils, but I’ve had experience with Grid dip meters and there are a few important issues that must be dealt with. One is, what happens to the unused coils when the equipment is not in use. They get separated from the equipment and

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2019-06-11 Selenium Rectifier Burned Up, How To Replace

from FB group Vintage Transistor Radios Jun 12 Bob Kirsch has the right idea, but the single replacement diode *must* be rated for 400 V peak inverse voltage or more. A 1N4007 is cheap and readily available. I assume you’re in a country where the AC line voltage is 120 VAC, because the rectified DC

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2019-05-31 DIY Plastic Variable Capacitor

I hear others complain about the high cost of variable capacitors, especially the older air variables with metal plates. So I decided to DIY and make one. This is my first attempt so forgive the lack of elegance and unfinished look. I’m sure it could be improved on and made better with some effort. The

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2019-05-26 Low Power AM Transmitter

I Can’t Find One I’ve seen several AM broadcast band transmitters on websites and on YouTube, but all of them require a 1 MHz oscillator module, which is difficult to obtain. I see modules for every other frequency not in the 550 to 1600 kHz AM band, but it seems all of the ones (and

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2019-05-19 No Go Showboat

from FB group regenerative receiver initiative May 22 Henrik Stenstrom I would like to build something hollow state with all sorts of gizmos like in this photo, but all of it would be a no-go showboat, just for looks. I would put Amber or orange LEDs under the tubes to make them look like they’re

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2019-05-09 A 3V to 9VDC Boost Converter V. 1.1

I built this in 2007. No load it puts out 9.5VDC and at 22 mA it puts out 8.5VDC. It works okay for powering a radio on the FM band, but it has too much RF Interference on the AM band. The original circuit had only a single output transistor but it couldn’t handle enough

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2019-04-08 Output Transformers Construction

from FB group Regenerative Receiver… Apr 8 庄议翔 The power transformers have the laminations interleaved. The first lamination has an E then I, the next one has I then E. So the transformer core does not have any air gaps, because it does not have any DC flowing through the windings. The transformers for single

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